The present invention relates to a car navigation unit for providing route guidance from a present position to a destination via a set desired en-route stop, and particularly relates to processing of the car navigation unit in a case where the vehicle has strayed from a guide route.
Car navigation units of related art normally have a function for detecting a present position, a function for, when a destination is inputted, searching for a guide route from the present position to the destination and the like. And while the vehicle is traveling, the guide route obtained by the searching and the present position of the vehicle are displayed on a display screen to provide route guidance.
Among car navigation units of this kind there are some with which, when a search for a route to a destination is carried out, to make it possible to set a course wished for by the driver, it is possible to input en-route stops. With a car navigation unit like this, when an en-route stop is inputted, a search for a route passing through this en-route stop is carried out, and consequently at times such as when the driver wants to make a stop en route or make a detour, or wants to set a route which passes through a desired location, this wish can be fulfilled.
In a car navigation unit with which it is possible to set en-route stops, when as shown in FIG. 7 a searched guide route R intersects with itself, it sometimes happens that at this intersection point C, due to the road to be traveled being mistaken or due to location error, the present position jumps from a route r1 leading to an en-route stop W to a route r2 of after passing through the en-route stop W. In this case, with a car navigation unit of related art, because it is inferred that a route change has been made and a switch is made to guidance for the route r2 of after passing through the en-route stop W, it becomes impossible to go to the en-route stop W.
In particular, when as shown in FIG. 8 the vehicle leaves an expressway H to call at an en-route stop W, enters the expressway H again through the same interchange as when it left the expressway H to go to the destination, the situation has often arisen due to location error that it is inferred that there has been a change from the route r1 leading to the en-route stop W to the route r2 of after passing through the en-route stop W, and the guide route is wrongly switched to the route r2.
This is because when a vehicle leaves an expressway H and enters an exit ramp of an interchange, since the branching angle of the exit ramp with respect to the expressway H is small, notwithstanding that the vehicle has left the expressway H and entered the exit ramp, it is readily determined due to location error that the vehicle is still traveling on the expressway H. And when it has been determined that the vehicle is traveling on the expressway H, it is assumed to have changed to the route r2 of after passing through the en-route stop W, and a switch is made to guidance for the route r2.
The present invention was made in view of the situation described above, and an object thereof is to provide a car navigation unit with which even when before passing through an en-route stop the present position has entered a guide route of after passing through that en-route stop, the guide route can to the utmost be prevented from being switched to the route of after passing through the en-route stop, and even if it has been so switched, it is to the utmost made possible to go to the en-route stop.
To achieve the object described above, in a car navigation unit according to the invention, when in a guide route the vehicle has strayed from a route of before passing through an en-route stop and moved onto a route leading to a destination of after passing through the en-route stop, if the distance from the present position of the vehicle to the en-route stop is below a predetermined value, travel guidance to the destination without passing through the en-route stop is carried out. According to this, even when travel guidance is carried out to the destination without passing through the en-route stop, because the distance from the present position to the en-route stop is a short distance below a predetermined value, if the driver wants to go the en-route stop, for example they can go to the en-route stop by looking at a map displayed on a display screen, and so even without route guidance there is no problem.
If, when in a guide route the vehicle has strayed from a route of before passing through an en-route stop and moved onto a route leading to a destination of after passing through the en-route stop, the distance from the present position to the en-route stop is above the predetermined value, it is desirable for a guide route leading to the destination via the en-route stop to be reset. By this means, the vehicle can be guided to the destination via the en-route stop because the guide route is not switched to the route of after passing through the en-route stop.
When in a guide route there is a point where guide routes of before and after an en-route stop is passed through intersect, at that intersection point it can be determined whether or not the vehicle has left the guide route of before the en-route stop is passed through and moved onto the guide route leading to the destination of after the en-route stop is passed through.
And, the above-mentioned predetermined value can be made the straight-line distance from the present position of the vehicle to the en-route stop. Also, when an en-route stop can be set by selecting from a telephone number, an address, a name of an establishment, or any point on a map displayed on display means, a construction may be adopted such that size of the predetermined value is set in correspondence with the en-route stop selection means.